Error inserting flatpickr in wordpress

I'm trying to insert flatpickr in wordpress but the calendar does not appear, only the "Select Date ..." appears. Does anyone know why? The code I am putting is this:

flatpickr("#inline", {
    inline: true,
    weekNumbers: true
})
<link href="https://unpkg.com/flatpickr/dist/flatpickr.min.css" rel="stylesheet"/>
<link href="https://chmln.github.io/flatpickr/bower_components/flatpickr/dist/themes/material_green.css" rel="stylesheet"/>
<script src="https://unpkg.com/flatpickr"></script><inputclass="flatpickr" type="text" placeholder="Select Date.." id="inline">